Although I would be hesitant to use any medications, first aid kits are very important. It is a good thing to have around.

I have meds for fungus, ich, 'mouthrot', finrot, parasites, slime coat impovement, etc. Not all my meds are suitable for my betta, though. I am not the person who would reallyknow exactly what meds are safe for betta, and which aren't.

I actually just did a lot of research on this for myself...I'll copy/paste my notes for you. All of this is used with bettas, though I stress following the directions on the medications as precisely as you can. most of this can be found at local pet and fish stores, and what can't can be found online. You don't have to have everything on the list, but most of it is helpful. I also recommend a plastic box to put everything in, as it's harder for pests to get into the medications that way.

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1. Quarantine Tank
separates your betta from tank mates, and allows you to do a full
change of everything in your regular tank while you treat your
betta. preferably unfiltered, as most medications will harm filters
or be absorbed by them. best around 2.5 gallons, though can be smaller
2. 1mL Syringe
helps measure proper dosages, easier to administer medicine
3. Heater
keeps tank at proper temperature
4. Water Conditioner
removes chlorines, chloramines, and other elements found in normal
tap water that are poisonous to fish. Should already be used daily.
5. Airpump w/ Stones
aeration helps bettas breath, as medicated water can make it hard
for bettas to get the air they need.
6. pH Test Kit
regulates pH of water
7. Ammonia Test Kit
regulates ammonia in water. too much ammonia can be poisonous
8. Nitrate Test Kit
regulates nitrates in water. again, too much can be bad
9. Aquarium Salt
aquarium salt helps prevent parasitic diseases like Ich and Velvet
good to use regularly
10. Betta Water
sold at some pet stores, this is clean, declorinated water with
minerals meant specifically for bettas. always good to keep a
bottle or two on hand, as tap water can sometime be polluted
beyond point where water conditioner can help.
11. Betta Fix
a safer version of melafix, with dosage appropriate for labyrinth
fish. however, be careful that you do not overdose, as some of the
ingredients can be lethal if too much is given
12. Tetracycline
broad spectrum anti-biotic for treating a variety of bacterial
infections
13. Ampicillin
broad spectrum anti-biotic for treating a variety of bacterial
infections. effective against most gram + serious infections, and
some gram - infections
14. Jungle Fungus Clear
treats minor bacterial infections. comes in blue tablets
15. Jungle Fungus Eliminator
treats minor bacterial infections. comes in yellow crystals in a
bottle
16. Melafix/Pimafix
antiseptic, speeds recovery and fights fungal infections. be very
careful that you do not overdose, as the melaleuca oil is lethal
to labyrinth fish like bettas if the dosage is messed up or if
treatment lasts longer than directed. suggested to be used after
fin rot is treated, as it will speed the regeneration of fins
17. Coppersafe
treats parasites like ich and velvet. contains a small amount of
"safe" copper, but can be poisonous if overdosed. lethal even in
prescribed doses to invertebrates (like snails), and may harm live
plants
18. Maroxy
treats fungal and bacterial diseases
19. Maracyn
treats body fungus, fin rot, popeye, gill disease, and other
infections caused by pathogenic bacteria. treats gram + infections
20. Maracyn II
treats dropsy, septicemia, popeye, and fin rot. treats gram - infections
21. Epsom Salt
treats constipation
22. Methilyn Blue
treats fungal infections, treats Ich, and is used for sterilizing
aquarium equipment like nets, decorations, etc.
23. Kanamycin
good for serious bacterial infections
24. Formalin
effective against parasites and ich. as it is a carcinogenic, it
can lead to death if instructions aren't followed.
25. Malachite Green
treats ich, parasites, and fungus, and diseases like columnaris. be
extremely careful not to overdose, as it will be lethal. in regular
doses, it will be lethal to plants and invertebrates like snails
26. Metronidazol
used to treat for protozoan-caused diseases and the control of
diseases caused by hexamita and spironucleus
27. Praziquantel
gentle treatment for tapeworm, flatworm, and flukes. unlilke most
other medications, if used as directed, it should not harm any
biological filtration
28. Fresh Garlic
boosts immune system and helps fights off parasites and diseases.
natural remedy
29. Frozen Peas
helps with constipation, and rumor has them helping prevent swim
bladder problems. also a good snack for bettas
30. Freeze Dried Bloodworms
natural food for bettas. seems to always work if they stop eating
31. Freeze Dried Daphnia
helps with constipation. natural food for bettas

Wow that is a list 0.o I should get some med on hand just in case I tend to keep aquarium salt and epsom salt, water conditioner, a extra heater, powdered fry food just in case, and extra pellet food. Extra containers. I live close to pet store so I can easily grab meds when I need them. I probably should.